WTP, I mostly agree, and I do TRY in my own posts (thanks to DY pointing this out to me a long time ago) to distinguish between something that is my opinion (based on experience, education, assumption or even feeling) and something that I can assert as fact (based on evidence, statistical or otherwise).
In my opinion, in most cases, something backed up by evidence makes a stronger argument, particularly in the Coffee Room, than something that is not backed up by such, even if it challenges widespread assumptions.